1. Field of the Invention
The present invention relates to a piezoelectric device and a method of production thereof.
2. Description of the Related Art
In inkjet heads, piezoelectric bodies and semiconductor devices such as FeRAMs and MRAMs, a piezoelectric film, a magnetic body and an electrode material such as platinum are used (refer to, for example, Japanese Patent Application Laid-Open (JP-A) Nos. 10-211701 and 2007-276384). These are called “hard-to-etch” materials and are difficult to process. In general, when a hard-to-etch material is processed, a dry etching process is frequently used. When a hard-to-etch material is etched, a gas containing halogen is frequently used. Examples of the gas containing halogen include mixed gases containing halogenous gases such as fluorine-based gases or chlorine-based gases and the inert gas argon, and mixed gases containing fluorine-based gases and chlorine-based gases.
When a piezoelectric film is dry etched, a resist is patterned on an etching surface to form a mask and dry etching is applied through the resist mask, whereupon a reaction product is generated at the time of etching which is non-volatile and tends to adhere to a side surface of the mask.
Furthermore, if over etching is performed, a lower electrode is sputter-etched and tends to adhere to a side wall of the patterned piezoelectric film. In this case, a film is formed by material adhering to a side wall of the piezoelectric film due to etching of a lower electrode (a film adhered to side wall). This film is electroconductive, and a leak current between a lower electrode and an upper electrode is therefore problematic. Various methods have been proposed to inhibit the upper and lower electrodes from short-circuiting due to the film adhered to the side wall.
JP-A No. 2000-22090 discloses a method in which, when an upper electrode, a ferroelectric material and a lower electrode are dry-etched, the upper electrode is dry-etched with an oxide film mask, an oxide film mask and a resist mask for the ferroelectric material and lower electrode are formed so as to cover the remaining oxide film mask, and the ferroelectric material and the lower electrode are then etched.
JP-A No. 2000-183287 discloses a method in which an inert gas and a halogen gas are used to etch a dielectric film formed on a lower electrode up to the middle thereof, followed by etching the remaining dielectric film and over-etching the lower electrode with only halogen gas, further followed by cleaning with a peeling agent such as water or hydrochloric acid to remove a residue generated by the etching.
JP-A No. 8-181126 discloses a method where, after an anti-etching mask is formed with SOG (Spin On Glass) or the like on a ferroelectric film such as PZT (lead zirconate titanate), an inert gas and a halogen gas are used to perform dry etching and a deposit adhered to a side wall of the ferroelectric film during etching is removed with water or the like.
According to the method disclosed in JP-A No. 2000-22090, an etching mask is formed a plurality of times and an upper electrode and a dielectric material are separately etched; accordingly, processing becomes complicated and costs increase greatly due to an increase in processing steps.
According to the method disclosed in JP-A No. 2000-183287, when a strong acid or a special peeling agent is used, a lower electrode and a dielectric film may be damaged. On the other hand, when water is used, a film adhered to a side wall may not be sufficiently removed.
According to the method disclosed in JP-A No. 8-181126, the processes involved in forming a mask increase because a hard mask is formed from SOG (or the process of forming a mask becomes complicated), and it is also difficult to remove a mask after etching.